1. Field of the Invention
This invention relates in general to systems for driving piles for on-shore and marine applications including the driving of bearing piles, fender piles and dolphins for mooring vessels.
2. Description of the Related Art
Cylindrical piles are conventionally driven into soil in both marine and on-shore applications through the use of steel mandrels which fit within the pile casings and receive repeated downwardly directed blows from hammers. The hammers can be of the diesel powered, pneumatic, hydraulic or gravity type. The hammer can have a hanging weight in the range of 16,000 to 100,000 lbs. and deliver impact forces in the range of 8,000 to 220,000 ft./lbs. Among the various types of piles in use today are cylindrical steel piles, wooden piles and pile casings which are composites of fiberglass and certain polymers. One such composite pile casing now in use is the Hardcore Fiberglass Tubular Piling.RTM., a product of Hardcore duPont Composites, L.L.C., which comprises E-glass directional reinforcement fiberglass with a vinyl ester resin matrix, non-woven Geotectile.RTM., polyethylene and UV inhibitors. The composite pile casings are supplied with outer diameters in the range of 8" to 18" or larger with a wall thickness varying from 0.18" to 0.46". The pile casings may also be tapered.
The tubular composite pilings are conventionally driven by means of the same equipment and methods used to drive steel and wooden piles, which essentially is by repeatedly beating the piles down by brute force. However, tubular pilings made of the above-described composite materials can be successfully driven to only a limited depth in the soil by using conventional equipment and methods. It would be desirable to provide a system and method of operation which would drive tubular composite piles deeper and thereby allow the piles to carry a greater design load. With the composite piles driven deeper, they can match the design loads achieved by steel piles. Because composite piles have only about 22% of the weight of steel piles with comparable load-bearing capacity, this would mean that the composite piles could be made cost competitive with steel piles by reducing the wall thickness and therefore reducing the amount and cost of the composite material.
U.S. Pat. No. 3,984,992 discloses a pile driving mandrel made of two arcuate segments which can be expanded into contact with the inside of a pile shell. However, the patent describes that the mandrel is for gripping a steel shell which is helically corrugated.
The need has therefore been recognized for a pile driving system and method which obviates the foregoing and other limitations and disadvantages of prior art pile drivers. In particular, there has not been provided an effective system and method for driving piles of composite materials in a manner which is competitive with steel piles. Despite the various pile driving systems and methods in the prior art, there has heretofore not been provided a suitable and attractive solution to these problems.